The present invention relates to a refractory plate assembly having therethrough at least one discharge opening and for use in a slide gate nozzle or sliding closure unit.
More particularly, the present invention is directed to such a refractory plate assembly for use as a stationary refractory plate or as a movable refractory plate and of the type including a supporting body which is provided with a separate member forming at least a part of the sliding sealing surface.
A sliding closure unit for the regulating of the flow of molten metal usually contains two closing plates formed of refractory material, one stationary plate and one movable plate, which abut on and coact with one another along respective sliding sealing surfaces. As is known, during operation these closing plates are subjected to high stresses, for example thermal stress, erosion, chemical attack, etc., such that the plates must be replaced periodically. However, depending upon the conditions of use, particularly on the type of molten metals involved, these stresses are completely different for different parts of the plates. In many cases, the important factor is that one or both of the closing plates be provided on their sliding sealing surfaces, or at least on parts thereof, with special properties, for example with respect to wear resistance, sliding properties, abrasion characteristics, heat conductivity, etc.
In the past, there have been proposals wherein a closing plate includes a refractory supporting body which is provided at the area of the sealing surface with a special sliding layer, for example Japanese Patent Publication No. 44-26935, West German DE-OS No. 1 935 424, West German DE-OS No. 1 937 742 and West German DE-OS No. 2 719 105.
However, according to these known arrangements, the sliding layer is rigidly and inseparably connected with the refractory supporting body. In other words, this known type of closing plate is designed as a composite body and can be replaced only in its entirety. The fabrication of such composite bodies however is very expensive and, due to the rigid bonding of the different materials usually having different coefficients of heat expansion, additional problems may arise.
Situations arise however where advanced wear or the like on the sealing surface member or on the sliding member limits the useful life of the entire plate, while the supporting body still would be usable. Under such conditions, the entire closing plate must be replaced. However, this obviously is not economical.